Methods for handling a bearingless machine

ABSTRACT

A method for handling a bearingless machine into a driveline includes coaxially aligning a rotor subassembly and a stator subassembly such that first and second circumferential track portions define a substantially complete first circumferential track in communication with a first portal. A first fixture band is inserted into the first circumferential track via the first portal to substantially maintain axial and radial alignment of the rotor subassembly relative to the stator subassembly.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority as a divisional application under 35U.S.C. §121 of earlier filed application Ser. No. 13/021,201, now U.S.Pat. No. 8,610,323 entitled “BEARINGLESS MACHINE” and filed on Feb. 4,2011 which is hereby incorporated by reference.

BACKGROUND

This invention relates generally to bearingless machines, and morespecifically to an apparatus and method for assembling, storing, andtransporting bearingless machines.

Bearingless machines, including Permanent Magnet (“PM”) motors andgenerators have been in use for many years. They have been favored overother types of electric machines for their efficiency, simplicity,robustness, and their tolerance to large radial air gaps between therotor and the stator. As is well known, the simplest forms of PMmotor/generators include an inner rotor assembly rotating concentricallywithin an outer stator assembly. The rotor assembly has one or morepermanent magnets with poles disposed diametrically about a rotor shaft.As the magnet(s) are rotated by motive power connected to the shaft, therotating magnetic fields generate an electrical current in one or moreadjacent winding circuits disposed circumferentially around the outerstator assembly. Similarly, currents induced in the winding circuitsinduce magnetic fields that can cause rotation of the shaft. A gearbox,such as a planetary gearset or other mechanical transmission can be usedto efficiently transfer rotational energy to and from the shaftdepending on the operating mode of the vehicle or other machine.

It is often desirable in manufacturing and logistics to provide completemodular components or systems as they move along the supply chain toimprove efficiency during the various stages of assembly. Transportationof these components is also helpful when these components or systems arecompact with a minimum amount of air or empty space being moved. Forexample, a bearingless machine can be transported from a supplier to thenext node in the manufacturing network with the rotating and stationarysubassemblies as separate entities. At the very least, this is a wasteof valuable shipping space given that the rotating subassembly is sizedto fit within the stationary subassembly. However, one or bothsubassemblies can be damaged without some way of keeping the rotorelement(s) separate from the stator elements.

SUMMARY

A method for integrating a bearingless machine into a driveline isdisclosed. The method comprises providing a rotating subassembly with afirst circumferential rotor track portion, providing a stationarysubassembly with a casing having a first portal and a firstcircumferential stator track portion. The method also comprises a stepof coaxially aligning the subassemblies such that the firstcircumferential track portion and the second circumferential trackportion define a substantially complete first circumferential track incommunication with the first portal. A first fixture band is insertedinto the first circumferential track via the first portal tosubstantially maintain axial and radial alignment of the rotorsubassembly relative to the stator subassembly. The rotor subassemblyand the stator subassembly are secured to adjacent components of thedriveline.

A method for handling a bearingless machine includes aligning a rotorsubassembly coaxially with a stator subassembly such that a firstcircumferential track is defined by circumferential rotor and statortrack portions. A first flexible cable is inserted through a statorcasing and into the first circumferential track coaxially between therotor and stator subassemblies. The first flexible cable is secured inthe first circumferential track to substantially maintain axial andradial alignment of the rotor subassembly relative to the statorsubassembly.

A method for repairing at least a portion of the driveline includesinserting a flexible portion of a first fixture band through a statorcasing into a first circumferential track. The first fixture band issecured such that the flexible portion is retained in the firstcircumferential track coaxially between the rotor subassembly and thestator subassembly. The rotor assembly is removed from a first portionof the driveline, and the stator assembly is removed from a secondportion of the driveline. At least one repair procedure is performed onat least one of: the first portion of the vehicle driveline, the secondportion of the driveline, and the bearingless machine. The rotorassembly is fastened to the first portion of the driveline, and thestator assembly is fastened to the second portion of the driveline. Thefirst fixture band is removed from the bearingless machine through thestator casing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically depicts a vehicle driveline with a permanentmagnet motor/generator between a prime mover, and a gearbox.

FIG. 1B is a magnified cross-section of the assembly shown in FIG. 1Awith the motor/generator disposed between the prime mover and thegearbox.

FIG. 2A shows a perspective of the permanent magnet motor/generatorshown in FIGS. 1A-1B.

FIG. 2B is a cross-section of the permanent magnet motor/generator shownin FIG. 2A.

FIG. 2C is an exploded view of the permanent magnet motor/generatorshown in FIG. 2A.

FIG. 3A shows an outer view of the permanent magnet motor/generator withtwo portals in the stator casing.

FIG. 3B shows a detailed view of two fixture bands for insertion intothe portals shown in FIG. 3A.

FIG. 4A depicts a driveline that includes the permanent magnetmotor/generator shown in FIG. 3A incorporated into a driveline with thefixture bands of FIG. 3B installed.

FIG. 4B shows a first radial cross-section of the assembly in FIG. 4A.

FIG. 4C shows a second radial cross-section of the assembly in FIG. 4A.

FIG. 4D is an axial cross-section showing placement of the fixture bandsrelative to the rotor and the stator.

FIG. 5A is a cross-section of alternative rotor and stator assemblyhaving an alternative fixture band disposed in the fan volute.

FIG. 5B is a cross-section of the alternative fixture band installed inFIG. 5A.

DETAILED DESCRIPTION

FIG. 1A depicts driveline assembly 10 with prime mover 12, gearbox 14,and permanent magnet motor/generator 16. Driveline assembly 10 istypically installed in a motor vehicle (not shown), such as a personalautomobile, a commercial transport, or a military vehicle. In oneexample configuration, prime mover 12 is an internal combustion enginepowered by hydrocarbon-based fuels such as diesel fuel, gasoline,kerosene, or compressed natural gas. Prime mover 12 can be any motorthat converts chemical energy of fuel directly into mechanical force.Power from prime mover 12 is provided to and from a plurality of wheelsand/or tracks (not shown) through gearbox 14. Additional power can beprovided to or from permanent magnet motor/generator 16, depending onits operating mode.

Prime mover 12 and permanent magnet motor/generator 16 provide power togearbox 14 through a shaft (shown in FIG. 1B). Gearbox 14 can be aplanetary gearset, a traditional multi-gear transmission, or othersimilar arrangement. In this example, permanent magnet motor/generator16 is installed between prime mover 12 and gearbox 14 and isconfigurable to alternately operate as a motor or a generator, dependingon the operating needs of the vehicle (not shown) and the mode ofoperation as described above. When motor/generator 16 is in motor mode,gearbox 14 is configured to efficiently combine and convert rotationalpower of prime mover 12 and/or permanent magnet motor/generator 16 intovehicular motion. When motor/generator 16 is in generator mode, gearbox14 can also be configured to convert energy from vehicle motion and/orfrom operation of prime mover 12 by capturing rotational energy of thetransmission shaft (shown in FIG. 1B).

In recent years, the automotive industry has started to favor permanentmagnet electric machines for vehicle propulsion applications. In theseapplications, the electric machine has been integrated into the vehiclepropulsion system with the engine and the vehicle transmission. Asdescribed above, the electric machine can be integrated in a mannersimilar to that shown in FIGS. 1A and 1B, with motor/generator 16disposed between prime mover 12 and gearbox 14. This exampleconfiguration can be seen in more detail in FIG. 1B.

FIG. 1B shows an enlarged cross-sectional view of driveline 10 centeredaround motor/generator 16. This figure includes prime mover 12, gearbox14, motor/generator 16, transmission torque converter 18, engine flexplate 20, motor/generator rotor 22, motor/generator stator 24, enginedrive shaft 26A, and transmission shaft 26B.

As was seen in FIG. 1A, motor/generator 16 is disposed between primemover 12 and gearbox 14. Specifically in this example, motor/generator16 is adjacent to torque converter 18 and engine flex plate 20 androtatably connected to each via shafts 26A and 26B. Transmission torqueconverter 18 is a well-known device to increase the torque available,particularly at low engine and vehicle speeds. Flex plate 20 is used inmany heavy-duty vehicles, including those built for industrial andmilitary applications. Flex plate 20 allows for angular misalignmentparallel to the axis of rotation between the transmission input shaftand the engine crank shaft. Flex plate 20 is generally very stiff in therotational direction of the engine, transmitting rotational torque whileallowing for deflections parallel to the axis of rotation of the enginebetween the engine and transmission. If the transmission shaft werebolted directly to the engine crank shaft without flex plate 20, thebolted joint would prematurely fail due to fatigue.

Permanent magnet motor/generator 16 includes rotor subassembly 22 andstator subassembly 24. Rotor subassembly 22 is coupled to prime mover 12by engine drive shaft 26A, such as by a plurality of bolts. In thisexample, gearbox 14 also includes shaft 26B coupled to the opposing faceof rotor subassembly 22. Shafts 26A and 26B cooperate to transfer powerbetween prime mover 12, motor/generator 16, gearbox 14, and the drivewheels (not shown). When operating in motor mode, motor/generator 16 andgearbox 14 can be configured as a starter to start prime mover 12 and/orprovide additional power to the drive wheels. In generator mode,motor/generator 16 can capture mechanical energy from prime mover 12and/or the drive wheels (via gearbox 14) to convert into electricalpower for vehicle accessories. Excess electricity generated can be sentto one or more storage devices, such as batteries and/or high-powercapacitors. Motor/generator 16 is seen in detail in FIGS. 2A-2C below.

FIG. 2A illustrates permanent magnet motor/generator 16 with rotorsubassembly 22 and stator subassembly 24. FIG. 2B shows an axialcross-section of permanent magnet motor/generator 16 with rotorsubassembly 22, stator subassembly 24, permanent magnets 28, stator 30,and air gap 32.

Rotor subassembly 22 rotates within stator subassembly 24 in either amotor mode or a generator mode described above. After permanent magnetmotor/generator 16 has been assembled, permanent magnets 28 arecoaxially aligned with stator 30 to maximize interaction between them,thus increasing efficiency of permanent magnet motor/generator 16. InFIG. 2B, it can be seen that permanent magnets 28 are disposed aroundthe outer periphery of rotor subassembly 22, and interact with coaxiallyadjacent stator 30.

FIG. 2C is an exploded view of motor/generator 16 shown in FIG. 2A withrotor subassembly 22, stator subassembly 24, permanent magnets 28, andstator 30. FIG. 2C shows how motor/generator 16 is assembled, whererotor subassembly 22 is placed coaxially within stator subassembly 24 toalign magnets 28 and stator 30 as described above.

The automotive industry has started to pursue the use of bearingless PMelectric machines, such as motor/generator 16. Early in the evolution ofintegrating motor/generators into vehicle drivelines, an electricmachine rotor was typically supported by its own dedicated set of rotorsupport bearings. In such machines, the bearings were installed betweenthe rotor and stator subassemblies. On PM electric machines that haverotor support bearings, the rotor is supported by assembly fixturesuntil the bearings are installed. Once the bearings are installed, theyaxially and radially support the rotor in its proper location.

It was found that these rotor support bearings were the least reliablecomponents of a PM electric machine. Thus, bearingless machines are morefrequently used to increase the reliability of the electric machine,while also decreasing its cost and complexity. However, bearinglesspermanent magnet motor/generators can be difficult to store, install,and transport, particularly when the electric machine is to be placedwithin the driveline rather than at one end.

During assembly of PM electric machines, such as motor/generator 16,forces generated between permanent magnets 28 and stator 30 must beaccounted for and reacted during assembly, storage, and transportation.For example, as rotor subassembly 22 and stator subassembly 24 arebrought axially together, as shown in FIG. 2C, magnets 28 on rotorsubassembly 22 are magnetically drawn radially toward stator 30. Thismagnetic force can exceed several hundred pounds. Since permanent magnetmotor/generator 16 does not have inherent fixtures like bearings,undesired contact and damage is likely due to the magnetic attractionbetween magnets 28 and stator 30. Similar damage can occur in these andother bearingless machines due simply to vibrations and sudden movementsexperienced during transport and installation.

Ordinarily during assembly of motor/generator 16 and during integrationinto driveline 10 (shown in FIG. 1A), an assembly fixture (not shown) isutilized to react these magnetic forces and move rotor subassembly 22into place coaxial with stator subassembly 24. This fixture supports andmaintains separation of the subassemblies until other fixtures ordevices can be used. For example, when motor/generator 16 is firstassembled, it is likely to be stored or transported before finalintegration into a vehicle driveline. Storage and transportation ofmotor/generator 16 is most space-efficient if it can be done with rotorsubassembly 22 in its coaxial position relative to stator subassembly24. Further, this support must be maintained until the rotor is fastenedto engine crankshaft 26A, and/or transmission input shaft 26B (shown inFIG. 1B). The subassemblies must also be supported when the shafts areremoved for any reason, such as maintenance or repair. This is toprevent misalignment and damage caused by axial or radial deflectionsuch as from the high magnetic forces described above.

When the electric machine is located on one axial end of the driveline,a series of wedges, or a cylindrical spacer have previously beeninserted between the rotor and stator subassemblies. Once the electricmachine is integrated, these spacers or wedges could be removed axiallywithout disassembling or otherwise removing components in the driveline.However, in situations where the electric machine is located between theinternal combustion engine and the vehicle transmission, such as inexample driveline 10 shown in FIG. 1A, there is no access to add orremove such wedges or spacers proximate air gap 32 once permanent magnetmotor/generator 16 is incorporated into driveline 10.

Wedges or spacers placed around the air gap between the rotor and statorand interfere with free rotation of the rotor if left in place duringoperation of the electric machine. Thus it would be helpful to accessthe area between the rotor and stator subassemblies through the statorcasing to insert and remove assembly fixtures. Assembly fixturesconfigured to be easily installed and removed through the stator casingwould also be useful. Several example embodiments are described indetail below.

FIG. 3A shows a magnified view of permanent magnet motor/generator 16.Permanent magnet motor/generator 16 has stator subassembly 24 withportals 34A, 34B, orifices 36A, 36B and stator casing 38.

Portals 34A, 34B include respective orifices 36A, 36B through statorcasing 38. Portals 34A, 34B with orifices 36A, 36B lead to respectiveinternal paths (not shown in FIG. 3A) between rotor subassembly 22 andstator subassembly 24. As will be seen in FIGS. 4B, 4C, and 5A, thesepaths are sized to allow insertion and removal of assembly fixtures,such as correspondingly shaped fixture bands or other similar devices.As will also be seen, rotor subassembly 22 and/or stator subassembly 24can be adapted to include one or more tracks that serve as the internalpaths described above. These tracks secure the assembly fixtures duringtransport and integration of permanent magnet motor/generator 16 intothe driveline. Examples of assembly fixtures are shown in FIGS. 3B and5B below.

Providing access to insert and remove assembly fixtures through thestator casing greatly simplifies assembly, storage, and transportationof motor/generator 16. When rotor subassembly 22 and stator subassembly24 are brought into coaxial alignment, the assembly fixtures can beinserted, allowing the jacking fixtures or other support structures(described above) to be removed. Because of the access provided byportals 34A, 34B, assembly fixtures can remain in place untilmotor/generator 16 is put into service. The assembly fixtures can remainin place even when motor/generator 16 is installed in the middle of thedriveline because the assembly fixtures remain accessible via portals34A, 34B. Assembly fixtures can also be reinstalled in portals 34A whenthe vehicle driveline is disassembled for service. This eliminates theneed for separate supports for rotor subassembly 22 and statorsubassembly 24, which reduces the equipment and number of steps neededto perform maintenance.

FIG. 3B depicts a pair of example assembly fixtures. Bands 40A, 40Brespectively include flexible cables 42A, 42B, handles 44A, 44B, andlocking plates 46A, 46B.

Bands 40A, 40B include flexible cables 42A, 42B. Cables 42A, 42B areinserted into portals 34A, 34B via orifices 36A, 36B (shown in FIG. 3A).Flexibility of cables 42A, 42B simplifies insertion and removal of bands40A, 40B into one or more paths around the circumference of rotorsubassembly 22, as shown in detail in FIGS. 4A and 4B. Bands 40A, 40Bcan also include handles 44A, 44B to further facilitate insertion andremoval. Locking plates 46A, 46B proximate handles 44A, 44B can be usedwith bolts or other attachment means to secure bands 40A, 40B to statorcasing 38 around portals 34A, 34B.

In this example, flexible cables 42A, 42B are coated withpolytetrafluoroethylene (commonly known as “PTFE” or “Teflon”) to beeasily inserted between rotor subassembly 22 and stator subassembly 24.Other examples of resilient, flexible, self-lubricating materials forcables 42A, 42B also include reinforced or unreinforced silicone resin.Alternatively, cables can be made of any nonmagnetic material and can beseparately lubricated to facilitate installation and removal frombetween rotor subassembly 22 and stator subassembly 24.

Cables 42A, 42B are shown in this example with a uniform circularcross-section. However, it will be appreciated that other forms arepossible for cables 42A, 42B. In one alternative example, shown in moredetail in FIGS. 5A-5B, a single cable is shaped with a substantiallyuniform cross-section to fit within the fan volute of certainmotor/generators with a built-in fan. In other examples, cables 42A, 42Bcan alternatively have non-uniform cross-sections, and be in the shapeof a series of segmented spheres or cylinders which are fused or strungtogether. These and other alterations to the form and number of bands40A, 40B can be made without departing from the scope and utility of thedevice.

As shown above with respect to FIG. 2C, once rotor subassembly 22 iscoaxially aligned with stator assembly 24, a large radial magnetic forcetends to pull the centerline of rotor assembly 22 off of the centerlineof stator assembly 24. Fixture bands 40A, 40B are simple, inexpensiveexamples of assembly fixtures that can be installed through statorcasing 38 via portals 34A, 34B. Once in place, bands 40A, 40Bsubstantially fix rotor subassembly 22 relative to stator subassembly 34in both the radial and axial directions. They can remain in place untilintegration into driveline 10 with prime mover 12 and gearbox 14 (shownin FIG. 1A).

FIG. 4A is a detailed view of completed driveline 10 with prime mover12, gearbox 14, permanent magnet motor/generator 16, stator subassembly24, portals 34A, 34B, and fixture bands 40A, 40B. Bands 40A, 40B eachhas respective handles 44A, 44B, plates 46A, 46B, and locking bolts 48A,48B.

Fixture bands 40A, 40B are fed into portals 34A, 34B on stator casing38. Once fixture bands 40A, 40B are in place, jacking fixtures are nolonger needed to maintain separation of rotor subassembly 22 and statorsubassembly 24. The rotor and stator can be bolted or otherwise fixed totheir final assembled orientation. Bands 40A, 40B can be removed bydisconnecting locking bolts 48A, 48B and pulling tangentially viahandles 44A, 44B. The location of bands 40A, 40B relative to rotorsubassembly 22 and stator subassembly 24 will be seen in more detail inFIGS. 4B-4D.

In this example, permanent magnet motor/generator 16 is integrated intodriveline 10 by bolting stator subassembly 24 to prime mover 12 andgearbox 14. Rotor subassembly 22 is coupled to the engine crank shaftand transmission shaft (shown respectively as shafts 26A and 26B in FIG.1B). After rotor subassembly 22 and stator subassembly 24 are secured,fixture bands 40A, 40B can be removed. This is done by disengaging bolts48A, 48B holding plates 46A, 46B to respective portals 34A, 34B onstator casing 38. Handles 44A and 44B are then pulled in the tangentialdirection until cables 42A, 42B are completely out of the tracks betweenrotor subassembly 22 and stator subassembly 24. Once fixture bands 40A,40B are removed, permanent magnet motor/generator 16 is no longerrestricted and is ready for operation.

Bands 40A, 40B allow permanent magnet motor/generator 16 to betransported in a compact and efficient manner to the next point in thesupply network. Bands 40A, 40B are inserted as described above and canbe retained in place until permanent magnet motor/generator 16 is readyfor final incorporation into driveline 10. Incorporation can occur atany facility so long as bands 40A, 40B are maintained in place untilfinal assembly occurs. Bands 40A, 40B can also be reinstalled prior tomaintenance or repair that requires disassembly of driveline 10. In thismanner, permanent magnet motor/generator 16 can be assembled,transported, and installed without magnetic forces between the rotor andstator causing contact or misalignment.

FIG. 4B is a first radial cross-section of driveline 10 taken throughline 4B in FIG. 4A. Driveline 10 includes prime mover 12 and permanentmagnet motor/generator 16. Motor/generator 16 has rotor subassembly 22,stator subassembly 24, permanent magnets 28, stator 30, fixture band40A, cable 42A, handle 44A, locking plate 46A, rotor guide bracket 50A,directional arrow 52, circumferential track 54A, and first junction 56A.

This cross-section is taken proximate permanent magnet motor/generator16 and first fixture band 40A closest to gearbox 14 (shown in FIG. 3A).As described above, fixture band 40A is installed into circumferentialtrack 54A by inserting flexible cable 42A through orifice 36A at portal34A on stator casing 38. Fixture band 40A is fed into motor/generator 16by inserting and sliding cable 42A in direction 52 until substantiallythe entire length of cable 42A is within circumferential track 54Abetween rotor subassembly 22 and stator subassembly 24.

Circumferential track 54A is the path by which cable 42A is guided andretained. In this example, track 54A is defined by two guide brackets,one each on rotor subassembly 22 and stator subassembly 24. Generally,the guide brackets include a portion of track 54A that corresponds topart of the shape of fixture band 40A. As will be seen below, when rotormagnets 28 and stator 30 are coaxially aligned, the guide brackets lineup such that the two track portions define track 54A. The edge of rotorguide bracket 50A is visible in FIG. 4B, but can be seen in more detail,along with the stator guide bracket, in FIG. 4D.

Orifice 36A provides a path for communication between portal 34A onstator casing 38 and track 54A (at junction 56A) located between rotorsubassembly 22 and stator subassembly 24. Junction 56A is the point atwhich cable 42A goes from orifice 36A into track 54A. In this example,orifice 36A is arranged substantially tangential to circumferentialtrack 54A at junction 56A. It should be noted that orifice 36A need notbe precisely tangential to track 54A, and may even be slightly curved.However, it will be apparent that too much curvature in orifice 36A canresult in problems with feeding cable 42A into and around curved track54A.

Here, the length of cable 42A is substantially equivalent to thecombined length of track 54A and orifice 36A such that the end of cable42A without handle 44A sits near junction 56A. Thus when fixture band40A is properly sized and installed, handle 44A and locking plate 46Asit flush against portal 34A and can be secured to stator casing 38 bybolts 48A.

FIG. 4C is a second cross-section of driveline 10 taken radially throughline 4C in FIG. 4A. Driveline 10 includes prime mover 12 and permanentmagnet motor/generator 16. Permanent magnet motor/generator 16 includesrotor subassembly 22, stator subassembly 24, orifice 36B, fixture band40B, handle 44B, locking plate 46B, second circumferential track 54B,second junction 56B, and stator winding slots 58. Stator windings havebeen removed from slots 58 to better illustrate other elements in thefigure.

This radial cross-section is taken across permanent magnetmotor/generator 16 to show fixture band 40B, which is positioned closerto prime mover 12. As described above, fixture band 40B is installedinto circumferential track 54B by inserting flexible cable 42B intoorifice 36B at portal 34B on stator casing 38. Fixture band 40B is fedinto motor/generator 16 by inserting and sliding cable 42B in direction52 until substantially the entire length of cable 42B is withincircumferential track 54B.

Like track 54A, circumferential track 54B is the path by which cable 42Bis guided and retained between rotor subassembly 22 and statorsubassembly 24. Track 54B is also defined by two guide brackets, oneeach on rotor subassembly 22 and stator subassembly 24. The edge ofrotor guide bracket 50B is visible in FIG. 4C, but can be seen in moredetail, along with the stator guide bracket, in FIG. 4D.

Orifice 36B provides a path for communication between portal 34B onstator casing 38 and track 54B (at junction 56B) located between rotorsubassembly 22 and stator subassembly 24. Junction 56B is the point atwhich cable 42B goes from orifice 36B into track 54B. Again, orifice 36Bis arranged substantially tangential to junction 56B on circumferentialtrack 54B. Similarly, orifice 36B need not be precisely tangential totrack 54B, and may even be slightly curved. However, it will be apparentthat too much curvature in orifices 36A (in FIG. 4B) or 36B can causeproblems with fully feeding cables 42A, 42B into tracks 54A, 54B.

Like cable 42A, the length of cable 42B is substantially equivalent tothe combined length of track 54B and orifice 36B. When installed, theend of cable 42B without handle 44B should sit near junction 56B whenhandle 44B and locking plate 46B sit flush against portal 34B. Band 40Acan then be secured to stator casing 38 at portal 34B by bolts 48B.

As will be seen more clearly in FIG. 4D, bands 40A, 40B are positionedin tracks 54A, 54B located on either axial side of rotor magnets 28 andstator 30. This can be seen in part in FIG. 4C with the removal ofstator 30, revealing that track 54B is disposed adjacent to statorwinding slots 58.

FIG. 4D is a detailed axial cross-section of a portion of permanentmagnet motor/generator 16. The figure includes rotor magnets 28, stator30, air gap 32, cables 42A, 42B, rotor guide brackets 50A, 50B,circumferential tracks 54A, 54B, stator guide brackets 60A, 60B, rotortrack portions 62A, 62B, and stator track portions 64A, 64B.

As was seen in FIGS. 4A-4C, cables 42A, 42B are disposed on opposingaxial sides of rotor magnets 28 and stator 30. In this example, bothcircumferential tracks 54A, 54B are partly defined by rotor guidebrackets 50A, 50B and stator guide brackets 60A, 60B. In this example,there are half circle tracks 62A, 62B on rotor guide brackets 50A, 50B,located on either side of rotor magnets 28. There are also half circletracks 64A, 64B on stator guide brackets 60A, 60B. These respectivetrack portions 62, 64 encompass round cables 42A, 42B aroundsubstantially the entire circumference of motor/generator 16.

This arrangement of fixture bands with cables 42A, 42B in tracks 54helps prevent both axial and radial displacement of rotor subassembly 22relative to stator subassembly 24. It also prevents and minimizes damageby helping to react the magnetic forces between magnets 28 and stator30. During insertion into tracks 54A, 54B, cables 42A, 42B can also beunder slight compression, to improve retention of bands 40A, 40B and toimprove absorption of the relative motion between rotor subassembly 22and stator subassembly 24. And they can be used in virtually anyposition in the driveline due to the tangential access provided throughthe stator casing as described above. Bands 40A, 40B are thus effectivethroughout transport, storage, and installation of permanent magnetmotor/generator 16.

While bands 40A, 40B are circular in FIG. 4D, it will be recognized thatother complementary shapes of the cable and track are also possiblewithout departing from the scope of the invention. For example,different shapes of cables 42A, 42B can be arranged to matchcomplementary tracks 54A, 54B. One alternative example of acomplementary cable and track pair is shown in FIGS. 5A and 5B.

Two bands 40A, 40B are often used on either side of rotor 28 and stator30 to prevent contact between them. During assembly and transportation,bending forces are likely to be relatively high, and it is difficult tomaximize alignment between rotor subassembly 22 and stator subassembly24 without them coming into contact.

While FIGS. 3A-3B and 4A-4D all illustrate two fixture bands, only oneband is required in certain circumstances. For example, where themagnetic attraction between rotor magnets 28 and stator 30 is relativelysmall, their axial width is relatively small compared to thecross-sectional area of the cable, or the air gap is relatively large,the risks of magnets 28 and stator 30 coming into contact are relativelyminor except when high bending or vibratory stresses are applied. Whenthe band is also larger and more resilient, such as is shown in FIGS. 5Aand 5B, only one such band may be required.

FIG. 5A is an axial cross-section of alternative permanent magnetmotor/generator 116. Motor/generator 116 has rotor subassembly 122,stator subassembly 124, rotor magnets 128, stator 130, air gap 132,alternative fixture band 140 with cable 142, along with fan volute 150.

As in the previous example embodiment, motor/generator 116 has two mainparts, rotor subassembly 122 arranged coaxially with stator subassembly124. Rotor magnets 128 are coaxially adjacent to stator 130 andseparated by air gap 132. In this alternative example embodiment,motor/generator 116 also includes fan volute 150 having rotor portion151 and stator portion 153 along with track 154.

Certain types of permanent magnet motor/generators include an integratedfan to improve cooling of the rotor and/or stator during operation.These are used, for example, when motor/generator 116 is capable ofgenerating or using high levels of current, which requires substantialairflow to facilitate cooling of stator 130. The fan includes fan volute150 located axially adjacent to stator 130. Fan volute 150 is defined byrotor portion 151 and stator portion 153. This is similar to thelocation of bracket 50A shown in FIG. 4D. Ordinarily, inmotor/generators without fans, this space is part of the air gap aroundthe stator.

When motor/generator 116 is being assembled, transported, or installedinto a driveline, rotor subassembly 122 is not rotating and fan volute150 is effectively empty space. A portion of this space can double ascircumferential track 154 for band 140, as shown in FIG. 5A. This issimilar to tracks 54A, 54B in FIGS. 4A-4D. Band 140 has cable 142 with across-section complementing the shape of track 154 to take advantage ofthat empty space. When installed in volute 150 as shown in FIG. 5A, band140 secures rotor subassembly 122 relative to stator subassembly 124 andprevents undesired axial and radial movement as described above.

Cable 142 can be a flexible non-ferrous metal, which is more resilientthan a resin-based cable. This more complex design and largercross-section of track 154 allows for a single band 140 to be placed infan volute 150, as compared to two bands 40A, 40B with round cables 42A,42B (shown in FIG. 4D). The more complex geometry, larger size, and moreresilient material of band 140 improves contact with rotor subassembly122 and stator subassembly 124 as compared to bands 40A, 40B shown inFIGS. 4A-4D. Fan volute 150 is also accessed by a portal in the casingsimilar to portals 34. It will be apparent that the portal and orificefor motor/generator 116 will not be round but instead will be shaped tocomplement the cross-section of cable 142.

FIG. 5B shows a cross-section of fixture band 140 having cable 142 withcorners 141 and cutouts 143. Band 140 is an alternative embodiment offixture bands 40A, 40B shown in FIG. 3B. This cross-section is generallyrectangular with square cutouts 143 on each corner 141. This allows band140 to fit securely into fan volute 150 as shown in FIG. 5A.

Thus far, the invention has been described relative to an example of apermanent magnet motor/generator being installed into a driveline of aground-based vehicle. It has also been described using the example ofthe motor/generator being installed into the center of a driveline.However, it should be noted that this specification should not be readto limit the claims to these example embodiments. A permanent magnetmotor/generator according to the above descriptions can be installed atthe end of a driveline without affecting the purpose or utility thereof.Similarly, it is not limited to application in ground-based vehicles.For example, in addition to stand-alone electric machines, otherelectric motor applications use a permanent magnet motor/generator orother similar apparatus as part of a larger electromagnetic generatorassembly. In one instance, a ram air turbine generator for an aircraftutilizes a permanent magnet motor/generator to generate exciter current,which is later applied to power an electromagnetic main rotor. Thefeatures described can be readily modified for the permanent magnetmotor/generator section of the ram air turbine generator duringassembly, transport, and/or installation.

The features shown and described in the specification can also beadapted to apply to any type of electric machine (e.g., induction,switched reluctance, wound field, etc.). It will also be appreciatedthat they can be used in applications other than electric machines. Forexample, any type of rotating hardware that doesn't have its own supportbearings, such as a turbine or compressor section of a gas turbineengine, can be adapted to include one or more fixture bands. The bandscan be used in a similar manner to retain the rotor section before thebearingless component is integrated with its permanent supportstructure.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

The invention claimed is:
 1. A method for integrating a bearinglessmachine into a driveline, the method comprising: providing a rotorsubassembly with a first circumferential rotor track portion, providinga stator subassembly with a first circumferential stator track portionand a casing having a first portal; aligning the rotor subassemblycoaxially with the stator subassembly such that the firstcircumferential rotor track portion and the first circumferential statortrack portion define a substantially complete first circumferentialtrack in communication with the first portal; inserting a first fixtureband into the first circumferential track via the first portal tosubstantially maintain axial and radial alignment of the rotorsubassembly relative to the stator subassembly; after the step ofinserting the first fixture band, inserting a second fixture band into asecond circumferential track via a second portal in the casing; andsecuring the rotor subassembly and the stator subassembly to adjacentcomponents of the driveline.
 2. The method of claim 1, furthercomprising the step of removing the first fixture band from the firsttrack via the first portal after the step of securing the rotorsubassembly and the stator subassembly.
 3. The method of claim 1,wherein the bearingless machine is an electric machine selected from oneof: a permanent magnet machine, an induction machine, a switchedreluctance machine, and a wound field machine.
 4. The method of claim 1,wherein the aligning step is performed by utilizing at least one jackingfixture to react magnetic forces between a plurality of rotor elementsdisposed in the rotor subassembly and a plurality of stator elementsdisposed in the stator subassembly.
 5. The method of claim 4, whereinthe jacking fixture maintains a substantially uniform annular air gapbetween the rotor elements and the stator elements until the firstfixture band is inserted into the first circumferential track.
 6. Amethod for integrating a bearingless machine into a driveline, themethod comprising: providing a rotor subassembly with a firstcircumferential rotor track portion, providing a stator subassembly witha first circumferential stator track portion and a casing having a firstportal substantially tangential to the first circumferential statortrack portion; aligning the rotor subassembly coaxially with the statorsubassembly such that the first circumferential rotor track portion andthe first circumferential stator track portion define a substantiallycomplete first circumferential track in communication with the firstportal; inserting a first fixture band substantially tangentially intothe first circumferential track via the first portal, to substantiallymaintain axial and radial alignment of the rotor subassembly relative tothe stator subassembly; and securing the rotor subassembly and thestator subassembly to adjacent components of the driveline.
 7. Themethod of claim 6, further comprising: after the step of inserting thefirst fixture band, inserting a second fixture band into a secondcircumferential track via a second portal in the casing, the secondportal substantially tangential to the second circumferential track. 8.The method of claim 6, further comprising the step of removing the firstfixture band from the first track via the first portal after the step ofsecuring the rotor subassembly and the stator subassembly.
 9. The methodof claim 6, wherein the bearingless machine is an electric machineselected from one of: a permanent magnet machine, an induction machine,a switched reluctance machine, and a wound field machine.
 10. The methodof claim 6, wherein the aligning step is performed by utilizing at leastone jacking fixture to react magnetic forces between a plurality ofrotor elements disposed in the rotor subassembly and a plurality ofstator elements disposed in the stator subassembly.
 11. The method ofclaim 10, wherein the jacking fixture maintains a substantially uniformannular air gap between the rotor elements and the stator elements untilthe first fixture band is inserted into the first circumferential track.